sudo apt-get install whowatch

Whowatch is an console, interactive users and process monitoring tool.It displays information about the users currently logged on to the machine, in real-time. Besides standard informations (login name, tty,host, userâs process), the type of the connection (ie. telnet or ssh) is shown. Display of users command line can be switch to tty idle time. Certain user can be selected and his processes tree may be viewed as well as tree of all system processes. Tree may be displayed with additional column that shows owner of each process. In the process tree mode SIGINT and SIGKILL signals can be sent to the selected process. Killing processes is just as simple and fun as deleting lines on the screen.

http://www.ubuntugeek.com/monitoring-real-time-user-logins-in-ubuntu.html

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